1. Field of the Invention
The invention relates to a tapered roller bearing.
2. Description of Related Art
As a rolling bearing configured to support a pinion shaft of a differential gear apparatus mounted in an automobile, for example, a tapered roller bearing described in Japanese Patent Application Publication No. 2015-169300 (JP 2015-169300 A) is known. The tapered roller bearing includes an inner ring 101, an outer ring 102, a plurality of tapered rollers 103, an annular cage 104, as depicted in FIG. 4. The tapered rollers 103 are interposed between the inner and outer rings 101, 102 in a rollable manner. The cage 104 holds the tapered rollers 103 at regular intervals in a circumferential direction.
A labyrinth clearance is formed between an inner peripheral surface 104a of a small-diameter-side end of the cage 104 and an outer peripheral surface 101a of the inner ring 101. A pump action resulting from rotation of the tapered roller bearing allows a lubricant to flow into a bearing interior through the labyrinth clearance. This allows suppression of excessive feeding of the lubricant to the bearing interior, reducing rotational resistance to the tapered roller bearing (stirring resistance of the lubricant).
In a tapered roller bearing configured to support a pinion shaft of a differential gear apparatus mounted in industrial equipment, the lubricant is less likely to be fed to the bearing interior. Thus, for the tapered roller bearing for industrial equipment, suppressing a rise in bearing temperature caused by insufficient lubrication is desired rather than reducing the rotational resistance to the bearing as described above.
An object of the invention is to provide a tapered roller bearing that allows suppression of a rise in bearing temperature caused by insufficient lubrication.
A tapered roller bearing in an aspect of the invention includes an inner ring having an inner-ring raceway surface, an outer ring arranged radially outward of the inner ring so as to be concentric with the inner ring and having an outer-ring raceway surface that faces the inner-ring raceway surface, a plurality of tapered rollers interposed between the inner-ring raceway surface and the outer-ring raceway surface, and a cage that holds the tapered rollers at predetermined intervals along a circumferential direction. A diameter of an inner peripheral surface of a small-diameter-side end of the cage is substantially the same as a diameter of a small-diameter-side pitch circle of the tapered rollers.